Natural gas is transported from place-to-place via pipelines. It is desirable to know with accuracy the amount of gas flowing in the pipeline, and particular accuracy is demanded when the fluid is changing hands, or “custody transfer.” Even where custody transfer is not taking place, however, measurement accuracy is desirable, and in these situations flow meters may be used.
Ultrasonic flow meters are one type of flow meter that may be used to measure the amount of fluid flowing in a pipeline. Ultrasonic flow meters have sufficient accuracy to be used in custody transfer. In an ultrasonic flow meter, acoustic signals are sent back and forth across the fluid stream to be measured. Based on parameters of received acoustic signals, the fluid flow velocity in the flow meter is determined. The volume of fluid flowing the meter can be determined from determined flow velocities and the known cross-sectional area of the flow meter.
The transit time of acoustic signals in an ultrasonic flow meter is a function of the speed of sound in the fluid. Temperature is one factor affecting the speed of sound in fluid. Consequently, an error in temperature measurement can result in undesirable inaccuracy in flow measurement. Therefore, techniques for identifying errors in measurement of temperature of fluid flowing through an ultrasonic flow meter are desirable.